Information system

ABSTRACT

An information system is provided for transmitting data into a local area surrounding the transmitter. The transmitter may be used to provide information to pedestrians, or to passing road traffic. Data is stored in a local memory  64  associated with the transmitter such that data stored in the memory can be repeatedly and frequently transmitted to users  70  having suitable reception apparatus  18  in the vicinity of the transmitter.

CROSS REFERENCE TO RELATED APPLICATIONS

This is a continuation patent application of U.S. patent applicationSer. No. 10/410,365 filed Apr. 18, 2003, which is a divisional patentapplication of U.S. patent application Ser. No. 09/680,348 filed Oct. 5,2000, now issued as U.S. Pat. No. 6,606,033, of which the contents ofboth applications are hereby expressly incorporated by reference herein.

FIELD OF THE DISCLOSURE

The present invention relates to an information system, and inparticular to a local information system which may be used bypedestrians or as a vehicle information system. Such an informationsystem maybe arranged to provide data concerning local services, mayallow local businesses to advertise or may advise the locally pertainingspeed limits to the driver of a vehicle. The system may be used in somepedestrian environments, for instance airports or railway stations, todeliver relevant contextual information such as timetables, arrival anddeparture data and so on.

BACKGROUND OF THE DISCLOSURE

There have been proposals to crack down on speeding. There has even beena suggestion of zero tolerance of minor speed violations. In the UnitedKingdom, the Council for the Protection of Rural England is calling fora 40 mph speed limit on rural roads. Reductions in speed limits on roadsare often largely ignored since drivers have become used to travellingon the road at the higher speed limit. Furthermore, local drivingculture may be such that speed limits are generally ignored. In the UKfor example, a great deal of motorway traffic travels at between 80 and85 mph.

Police forces have already installed speed cameras in order thatspeeding motorists can be photographed and have points awarded to theirlicence or fines imposed without the need for intervention by apoliceman. Conventional film based cameras have tended to have a marginof tolerance set into them in order that they only catch the worstoffenders and thereby can be expected to have a reasonable lifetimebefore the film needs replacing. Film based cameras are slowly beingreplaced by digital cameras which do not have the same data storageproblems. Furthermore, if the cameras have a telecommunications linkthen they are able to capture an image of every speeding vehicle thatgoes past them. If such cameras are set to a zero tolerance limit, itbecomes entirely feasible for a driver committing only minor speedingoffences to achieve sufficient speeding violations within a singlejourney to lose his license without him ever being aware of it.

Such a zero tolerance regime might result in many drivers spending aconsiderable amount of time looking at their speedometer andconsequently less time looking at the road. Furthermore, excessivelycautious drivers may drive at a larger margin below the actual speedlimit causing unnecessary congestion, possibly frustration amongst otherroad users and even additional accidents.

For the rigid enforcement of speed limits, there are two numbers thatthe driver needs to know. These are what the local speed limit is, andthe vehicle's speed is. Whilst the UK has, in general, a reasonably goodsign posting system, it is always possible to miss a road sign when thedriver's attention is directed elsewhere. This may be because of localtraffic conditions requiring driver attention. Furthermore, it is notuncommon, especially on rural roads, for road signs to become obscuredby overhanging trees in the summer or to appear as silhouettes whendriving into bright sunlight. There has also been a tendency to increasethe number of roadside signs, and this may increase further if roadsideadvertising or sign sponsorship is allowed, thus giving the driver farmore peripheral and nonessential information to sift through before hecan identify the local speed limit.

In the car, the speedometer is the most visible of instruments, but itis still provided in an instrument binnacle which requires the driver toavert his eyes from the road and to refocus on the distance to a fewfeet in front of him in order to read the vehicle's speed. Often anexperienced motorist knows his approximate speed by the sound of theengine of his car. Where some minor speeding is tolerated, this is asufficiently accurate technique for a motorist to regulate his roadspeed. However, if a zero tolerance regime is enforced, then themotorist can no longer rely on this audio clue, and will be forced toexamine his speedometer far more frequently and consequently be lookingat the road less frequently.

SUMMARY OF THE DISCLOSURE

According to a first aspect of the present invention, there is provideda vehicle information system comprising a receiver responsive to localdata transmissions from roadside transmitters and an audio and/or visualcommunications device for communicating information to a vehicle'soccupant.

It is thus possible to provide an information system which is responsiveto roadside transmitters in order to capture and hold data which may,for example be indicative of the local speed limit. Preferably theinformation system is arranged to receive broadcast data representativeof at least a local speed limit. The information system, or some othervehicle system, can be arranged to compare this speed limit informationwith locally derived data representative of the vehicle's speed and toindicate to the occupant, preferably the driver, the result of thecomparison. Thus, for example, a warning may be issued to the driver ifhe is at or exceeding the speed limit. Additionally, an advisory warningmay also be issued if the driver is close to the limit, for example inexcess of 95% of the speed limit. Additionally or alternatively datarepresenting the local speed limit may be provided to a vehicle's enginemanagement system or cruise control system so as to cause the vehicle toautomatically stay within the speed limit until the driver intervenes todeliberately exceed the limit for example by switching the speed controlsystem off or by “kicking down” the accelerator in a manner similar tothat used to force a gear change in automatic vehicle boxes.

Preferably the receiver is a forward looking receiver. The receiveradvantageously has a narrow acceptance aperture such that it issubstantially responsive only to signals coming from an expecteddirection with respect to the vehicle. Thus if the receiver has arestricted acceptance aperture in the horizontal plane it can bearranged to receive data from roadside transmitters as the vehicleapproaches them. The acceptance in the vertical plane may need tosubtend nearly 90° such that it can accept signals from transmittersmounted near the roadway or on buildings or on gantries extending overthe road. In the UK, where vehicles travel on the left hand side of thecarriageway, the receiver may be squinted to look towards the left to aposition where traffic information signs are normally located. In otherjurisdictions, the receiver's antenna may have its primary lobe angledto the right.

Preferably the transmitter is arranged to transmit data representativeof one or more of the local speed limit, distance to the nexttransmitter, emergency text messages, geographical data, transmitteridentity data, local community data and advertisement data. This listshould not be considered exhaustive.

Advantageously, in a radio or microwave based system, only a limitednumber of radio channels or microwave channels would be required due tothe limited transmission range associated with each transmitter. In apreferred embodiment of the invention only one transmission channel(frequency) is required. This has the advantage of simplifyingmanufacture of the vehicle information system and enable communicationbetween parts of, or parties using, the system, i.e. car to roadside,roadside to car, police to car, police to roadside and so on. Howevertransmissions from vehicles to the roadside could be on differentfrequencies to transmissions from the roadside to vehicles.

By providing data indicating the distance to the next transmitter, thesystem can perform an integral data validity check to estimate if thecurrent speed limit is likely to be valid. Thus if the distancetravelled from the last transmitter to the present location exceeds thedistance indicated as being the valid distance to the next transmitter,the system can assert a signal to indicate that the speed limit datathat it currently holds should not be considered as accurate and thedriver can then act accordingly. Additionally, a road side transmittermay be arranged to transmit a plurality of distance validity messages.These messages may be associated with directional information which canbe interpreted with the aid of an on board direction detection system,such as a compass. The messages may also be associated with transmitteridentity codes. In an extension of such a system, the system might alsotransmit the distance to side roads or junctions in order that warningsmight be issued upon approach to a side road or junction. Additionally,such a system may also transmit data concerning the speed limitpertaining on that side road such that the driver or vehicle systems arepre-warned.

Advantageously, the signal transmitted by the roadside transmitters alsoprovides some form of direction indicating or carriageway coding signalin order to alleviate potential problems from multiple reflections.Consider a carriageway that runs north-south. A vehicle travelling northshould expect to receive data only from those transmitters morenortherly than it. The transmitters for a northerly travelling vehiclewould, of course, be facing south. Similarly, vehicles travellingsouthwards would expect to receive data from northward facingtransmitter. However there is a potential that as a southward travellingvehicle approaches a northward facing transmitter, radiation reflectedfrom the southward travelling vehicle could then be propagated towards avehicle travelling northwards. Such a vehicle could then be presentedwith wholly inaccurate data. In order to overcome this problem, adirection signal may be incorporated, for example a compass bearing orrange of compass bearings, such that vehicles travelling in thatapproximate direction know that they can accept the data transmissionsas being valid, whereas vehicles travelling outside of that range ofdirections ignore the transmissions. Additionally, or alternatively alane identification signal may be transmitted such that vehiclestravelling along one carriageway respond to one of the laneidentification signals and ignore data carrying an alternative laneidentification signal. Additionally or alternatively, each transmittermay transmit its own identity code and may also transmit the identitycode or codes of the succeeding transmitter or transmitters. Thus thevehicle's receiver is set up only to respond to the identity code of thenext valid transmitter. In a variant of this system, each transmittermay transmit the identity codes of the adjacent transmitters of theneighbouring carriageway such that the vehicle is programmed to ignoretransmissions emanating from those transmitters.

Capturing a transmitter identity code and associated positionalinformation has further advantages. Given that the position of thetransmitters are well known (because they are static objects for exampleaffixed to road signs bridges or buildings) each transmitter can becorrelated with its geographical position and acts as a way point.Vehicle navigation systems can then be programmed to navigate byreference to the transmitter identity codes. Such a system can be usedas an adjunct to or alternative to GPS based systems. Advantageously thetransmitters transmit their positional information in an explicitformat. Thus for example each transmitter may transmit its latitude andlongitude in a word such as:

-   -   <NAVWGS, LAT=51, 35.005N, LONG=05, 12.345W>        where:    -   NAV indicates that positional information follows    -   WGS identifies the format of the information:    -   LAT=latitude    -   LONG=longitude.

Alternatively, where local mapping authorities have developed their ownalternatives for specifying positions these can be used. Thus analternative word might be:

-   -   <NAVUKMAPOS, SU 987123>        where:    -   UKMAPOS specifies the coordinate system used on the ordnance        survey maps in the UK,    -   SU specifies the map area and the final 6 digits is a standard 6        digit positional reference.

As a further alternative, positional data may be given in a humanreadable form, for example:

-   -   <NAVTEXT, Passing through Kenton, South on A379>

Navigational systems based on the transmitter identity codes or explicitposition data can be expected to outperform GPS based systems in urbanareas where a GPS receiver may not be able to view sufficient GPSsatellites simultaneously in order to calculate its position.Furthermore, GPS needs a digital map to convert its information intousable navigation data, and will fail in tunnels and intermittently inbuilt up areas.

In contrast, urban areas are normally densely populated with sign postsso that the local transmitters can be arranged at frequent intervals.

Preferably a facility is also provided for local authorities andemergency services to add messages. Thus the police could introducelocal speed limits in response to adverse road conditions or accidents.Similarly, a local authority and the community could piggyback localinformation into the system and traders could advertise their presenceto passing motorists. The information that the transmitter is totransmit may be stored in a local memory, that is cached, and can beperiodically updated.

Preferably the vehicle's information system also includes thetransmitter. The transmitter may be used to identify the vehicle to theroadside receiver as the vehicle passes it. The or each roadsidetransmitter receiver unit may then be arranged to pass vehicle identityinformation or other data into a telecommunications network. Such asystem may be used by fleet operators in order to track the location oftheir vehicles. Additionally or alternatively, security companies mayalso use it to track delivery vehicles or stolen vehicles. In a furtherextension of the system, once a stolen vehicle has been located,adjacent roadside transmitters may be arranged to transmit a disablecode targeted at that vehicle in order to cause the vehicle's enginemanagement system or other system to limit the vehicle speed or to shutit down completely. Advantageously the retransmit feature and responseto certain instructions can be wholly or partially disabled undercontrol of the driver, although deactivation may require the use ofsecurity means, such as passwords.

The system may also be used for automatic road tolling or controlledaccess to roads or spaces, such as car parks.

The system might further be used as an alarm, with a driver operatedpanic button being located within the passenger compartment. Thus thedriver may activate a panic button to assert an emergency signal inthose situations where the driver feels worried or intimidated, butnevertheless wishes to keep the vehicle moving, for example a road rageincident. A further panic button, or an output from a vehicle monitoringsystem such as an engine management system, deceleration sensor or airbag activation system, may be used to initiate an emergency broadcastmessage if the user or an automated system deems it appropriate.

Such a system may further be adapted to automatically transmit to theauthorities when a speed violation above a certain threshold hasoccurred. Thus there is potential for a vehicle fitted with the systemto automatically inform the authorities when the driver is speeding.

Preferably the data links between the roadside transmitter and the carare infrared or microwave links as these can be arranged to give line ofsight coverage, thereby providing only local coverage. However, it isexpected that microwave technology would be preferred as this has thepotential to function in the mornings and the evenings when the sun islow at the horizon and might otherwise wash out infrared communicationlinks.

Additionally or alternatively, magnetic data links may be provided. Thustransmission coils may be embedded adjacent to the road or in the roadsurface in order that vehicles can communicate with the coils as theypass over or adjacent them.

Advantageously a vehicle fitted with the system may also have a rearfacing transmitter in order that it can transmit messages to a vehiclefollowing it. Such a system may be used to daisy chain messages.Additionally or alternatively, the system may be used to enhance roadsafety. For example, a car fitted with the system may also include anaccelerometer or other system able to judge when the car is undergoingsevere braking, as might incur in an emergency situation. A messageindicative of this may then be transmitted to following cars in orderthat the drivers can be alerted promptly or that in-car systems takecontrol of the following vehicles and automatically decelerate them inorder to reduce the chances of an impact.

Advantageously, each transmitter may be arranged to have a quiescentmode in which it transmits a carrier signal, possibly in associationwith other data, and vehicles and road side units can use the Dopplershift of the signal to estimate the vehicle's speed and/or relativespeed. This speed data, and rate of change of speed data may be used tojudge when a vehicle is speeding and/or undergoing rapid deceleration.Advantageously forward facing transmitters are distinguished from rearfacing transmitters by identity codes thereby enabling an on board dataprocessor to distinguish between signals from vehicles travelling in thesame direction and those travelling in the opposite direction. Thecarrier signal may be transmitted continuously, or discontinuously butfrequently.

The transmitter may also act in a RADAR mode, using microwave traveltime to a vehicle and back to provide an estimate of range. The signalsmay be passively returned from vehicles, i.e. reflected, or activelyretransmitted with data identifying the propagation delay introduced bythe transmitter and receiver of the vehicle actively returning thesignal.

According to a second aspect of the present invention, there is provideda roadside transmitter for use in association with a in-vehicle datasystem, the transmitter being arranged to transmit local road data topassing vehicles.

Advantageously a receiver is also provided, optionally in the road sidetransmitter, for receiving data transmitted from passing vehicles.Preferably the road side transmitter and receiver are associated with acontroller which is also connected to a telecommunications network forexchanging data with a remote site.

According to a third aspect of the present invention there is provided alocal area information system, comprising data transmitters having amemory for storing information relating to the local area and aplurality of user devices for receiving data from the transmitters andpresenting the information to a user.

According to a fourth aspect of the present invention there is provideda transmitter for a local area information service, the transmittercomprising at least one of a microwave, radio, or ultrasonic or infraredtransmission device, and a memory for storing information, saidinformation by repeatedly retransmitted by the transmission device.

According to a fifth aspect of the present invention, there is provideda receiver responsive to data transmissions from local transmitters, andfor storing the information in a local memory such that a user canselect the information for presentation to the user.

It is thus possible to provide a information system which can provideinformation pertaining to the local area to a user. In particular theinformation may include advertisements from local shops or nationalbrand owners.

The local transmitters maybe in the form of posts or small transmittersattached to buildings or street furniture. Thus the information could betransmitted into a very small cell indeed, perhaps only of the order of10's of meters across.

Advantageously the receiver constituting an embodiment of the presentinvention comprises a display device in co-operation with a local dataprocessor. Indeed the receiver may comprise a portable computing device,such as a personal digital assistant or palmtop computer. Such a devicecan function in a pedestrian environment, and may also be used withinthe automotive environment.

Thus a single receiver or display device thereof can constitute a commoncomponent in an embodiment of the receiver according to the first aspectof the present invention and of the fifth aspect.

Indeed, it is expected that a device such as a small computer, personaldigital assistant or the like may be used in a docking station when in avehicle so as to receive data from the in vehicle receiver ortransponder and to display it to the occupants of the vehicle. However,the same device may be removed from its docking station and use aninbuilt receiver or infrared port, or dock with portable receiver ortransponder module, to allow information to be delivered in a pedestrianenvironment, such as shopping complexes, airports, bus stations, trainstations, hotels, streets and the like.

The high data rates that can be supported in the local regions aroundeach transmitter enables a vast amount of data to be transmitted to thereceiver very quickly. Thus a user can quickly receive the data aboutproduct prices or promotions offered by a business. The data may beorganised in a book like or other browsable form such that the user cansift through the information to select those portions of interest.

Preferably the receiver can also transmit data to the local areatransmitters, and these are connected to a communication system suchthat enquiries can be made concerning information not stored in thememory of the local transmitter, but such that the information can beaccessed via a broader network of computers. Thus a user is able toaccess data across, for example, the Internet.

Preferably the receiver's bidirectional communication link with thelocal area transmitters has sufficient bandwidth to support voicecommunication either in place of or simultaneously with data and/orvideo transmission. Thus the hand held receiver can act to accept datafrom the local transmitter for which the recipient need not pay, andalso make use of more specific services such as internet access, voiceor videophone for which the user may pay or may not pay.

Thus a receiver constituting an embodiment of the present invention mayprovide the functionality of the WAP mobile telephone. However, whereasa WAP telephone user has to dial out to browse the internet to obtaindata such as local restaurant menus, bus time tables and so, the presentinvention makes that information continuously available from the localtransmitters.

The information may be categorised by topic using embedded tags, such asmeta tags, which may be used to present data to the user in a structuredmanner. Since the memory capacity of the local transmitter may be largerthan that of the receiver unit, the receiver may conserve its memoryresource by capturing only portions of the data, such selection beingdone on the basis of the embedded tags. The high repetition rate of datatransmission from the local transmitter ensures that the data which wasnot captured will be available without a significant delay should theuser become interested in it.

According to a sixth aspect of the present invention, there is provideda method of making data available to at least one user, the methodcomprising the steps of holding data in a memory within a transmitterarranged to transmit data in a region surrounding the transmitter; andrepeatedly transmitting the data held in the memory into the region suchthat a suitable receiver within the region can make the data availableto a user.

Preferably the data is categorised such that it is presented in asortable or indexed format.

Preferably the data includes advertisements.

Preferably the advertisers pay for advertising “space” so as tosubsidise, or render free, the cost to the user for receiving some orall of the data transmitted from the transmitter.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will further be described, by way of example, withreference to the accompanying drawings, in which:

FIG. 1 schematically illustrates a vehicle approaching a roadsidetransmitter;

FIG. 2 schematically illustrates the components within an in-vehicleinformation system;

FIG. 3 schematically represents a data word used by an embodiment of theinvention; and

FIG. 4 schematically illustrates a data system for use in a pedestrianenvironment.

DETAILED DESCRIPTION OF THE DISCLOSURE

As shown in FIG. 1, a roadside transmitter 2 constituting an embodimentof the present invention is located adjacent a carriageway such that itemits a well defined radiative beam 4 which can be received by oncomingvehicles 6. The radiative beam 4 is ideally transmitted in the form of anarrowly diverging cone such that it is only received by oncomingvehicles and has little chance of being received by vehicles travellingon the other carriageway. The vehicle 6 carries a directional antenna,schematically illustrated as 8 which faces forwardly, but may be angledto one side slightly in order to face the expected direction of theoncoming transmitters as the vehicle travels. The transmitter 2 may beplaced on any convenient housing or support beside the carriageway, butmost conveniently may be incorporated within pre-existing streetfurniture such as road signs, or “belisha beacons” used to signal thepresence of pedestrian crossings. When the transmitter is associatedwith a pedestrian crossing, for example an automated pedestrian crossingwhere the pedestrian must request permission to cross the road and thenis expected to wait until traffic lights have inhibited oncomingtraffic, the transmitter may be arranged to set a special signalindicating when the lights are red. Similar systems may be incorporatedwith traffic lights in order to reduce the likelihood of a driverjumping the lights. The forward facing antenna is connected to areceiver 10 which may optionally include a transmitter. The receiver 10is connected to a data processor 12 which is also arranged to receiveother signals from vehicle systems, for example an indication of currentvehicle speed via input line 14 or a signal from a panic switch viainput line 16. Other signal inputs may be provided. The data processor12 is arranged to receive signals from the receiver 10 indicating thecurrent speed limit and the distance to the next transmitter. Using aninternal clock and the speed information, the data processor 12 is ableto integrate the speed with respect to time in order to determine thedistance travelled by the vehicle since it passed the last transmitter.The transmitter's signals may be receivable by the vehicle over a rangeof several tens of metres as it approaches the transmitter. Neverthelessthe data-processor 12 can accurately estimate when the vehicle is aboutto pass the transmitter since the signal will abruptly fade to zero. Thedata processor can use this as an indication that it should now startits distance travelled calculations in order to determine when it shoulddetect the next transmitter 2. The data-processor 12 is also arranged tocompare the current speed with the limit speed and to issue a warning toa driver via a communications device 18 in the event that the driver isexceeding the speed limit. The communications device 18 may emit anaudible tone whose frequency or amplitude may vary with the severity ofthe amount by which the driver is exceeding the current speed limit.

Advantageously the system is arranged to transmit an unobtrusive andintermittent rest tone to indicate to the driver that the system isworking and that it regards its current data as being in good order. Thecommunications device 18 may also include a display screen or othervisual display (for example a head-up display) such that text messagescan be presented to the driver. The text messages could warn of adverseroad conditions, such as flooding or other obstructions on thecarriageway. Such messages would by their very nature be delivered localto the obstruction and would therefore be credible and be responded toby the driver.

The data processor 12 may also be arranged to communicate with a secondtransmitter 20 having a rear facing antenna 22. The data processor maybe arranged to daisy chain some of the signals it receives byre-transmitting them via the rear facing antenna 22. Additionally thevehicle 6 may carry a deceleration monitor such that emergency brakingof the vehicle can be detected. The data processor 12 may be responsiveto this emergency deceleration signal and may transmit a signal tofollowing vehicles indicative that its vehicle is undergoing heavybraking. Vehicle control systems of vehicles fitted with this system maybe arranged to undertake preventative actions and to decelerate thevehicle in the event that they receive such an emergency heavy brakingsignal from a preceding signal. A receiver may be associated with therear facing antenna 22 such that, for example, law enforcement vehicleschasing a stolen car may transmit instructions to the vehicle's enginemanagement system in order to degrade its performance, issue an alert tothe driver, or switch the vehicle's engine off.

FIG. 3 schematically illustrates a data word which may be transmitted bythe roadside transmitters 2 and received by the vehicle 6. The data wordadvantageously starts with-a start of message marker 30 in order thatthe data processor 12 can synchronise with the word. Following the startof message marker, a transmitter identity 32 may be transmitted whichenables the vehicle to ascertain where it is. In the event that avehicle fitted with this system breaks down, the driver may obtain fromthe information system the identity of the last transmitter that itpassed and this information can be relayed to the recovery services inorder that the position of the vehicle can be identified with greataccuracy. Following the identity code 32, the local speed limit “limit”is transmitted in word 34. This word is captured by the data processor12 and latched until such time as it is updated by the next transmitterthat the vehicle passes or becomes expired due to time or distancetravelled. The next word 36 gives an indication of the distance from thecurrent transmitter to the subsequent transmitter. As notedhereinbefore, the vehicle can then calculate the distance that it hastravelled in order to determine if its current speed limit can still bebelieved, i.e. because it has covered less ground than the distancecontained in word 36, or if it has travelled significantly further thanthat distance, to indicate that it has lost the local speed limitinformation. Word 38 is reserved for emergency messages which may betextural messages presented to the driver. However, if word 38 includesits own start and end of word markers such that it can be of any length,then audio messages can be transmitted. Additionally, a predefined setof textural and audio messages may be stored in the information system,and an identity code may be transmitted in word 38 in order that thecorrect message is selected and played to the driver. Finally, anadvertisements and/or commercial information field 40 is provided beforethe end of message marker 42.

Each transmitter 2 may be connected to a local controller (not shown) ora remote controller (not shown) via a communications link, such as thewire link 50 schematically illustrated in FIG. 1. However radiotechnology, for instance cell phones, may be used to link the roadsidetransmitter and associated data processor to a control node.

In systems employing bidirectional communication, the data processor 12may be arranged to transmit a vehicle identity via a forward facingtransmitter and forward facing antenna to the roadside unit 2.Alternatively a vehicle can use a rear facing transmitter. Thus such avehicle receives information as it approaches a roadside unit and sendsinformation after it has passed the roadside unit. This can thencommunicate with its local controller in order to indicate whichvehicles have passed it and what time. The vehicle may optionally signalits speed and whether its driver has committed a sufficiently grossspeeding offence for this to be automatically notified to theauthorities. This data can then be made available in order that vehiclescan be tracked.

Advantageously the or each roadside transmitter incorporates a roadsidedata terminal or communications port such that the relevant authoritiescould perform in situ reprogramming of the speed limit or other messagesdelivered from the unit to oncoming vehicles. Additionally the primarymicrowave link to vehicles could be used by police or other authoritiesto update the transmitter with messages written from authorised vehicleswhen they are near or passing a road side unit. Security codes canensure that only the authorised person can change the messages.

In order to overcome problems of reflected signals, a valid directionsignal may also be included. The signal may transmit minimum and maximumbearings through which its speed data can be regarded as valid, or maytransmit a nominal direction and upper and lower limits such thatvehicles travelling within the bearings defined by this range can regardthe incoming data as valid. In order to use such a system, the dataprocessor 12 would need to be responsive to a magnetic compass such as asimple two axis flux gate compass which could be integrated easily intothe vehicle.

Signals from roadside transmitters when direction information isunambiguous may be arranged to transmit specially coded information inorder to allow on board compasses to undergo calibration.

Advantageously the transmitters retransmit their data regularly, forexample every half a second, such that a vehicle approaching a signshould have multiple opportunities to capture the incoming data.

In embodiments of the invention in which the vehicle is allowed to daisychain the signals, the data processor is ideally arranged to generate arandom delay period before re-transmitting the information. Theintroduction of a random delay should ensure that two vehicles do notrepeatedly attempt to transmit at the same time to other vehicles. Inthe event that multiple broadcasts are received simultaneously or nearsimultaneously, the data processor may be arranged to perform somearbitration algorithm in order to decide which message it will relyupon. In embodiments of the invention where a vehicle is allowed todaisy chain messages, a further algorithm is employed within each dataprocessor to enable the control of the geographical extent of any daisychain alarm message. The originating vehicle of the message will includea data tag within the message which indicates the time that the messagewas sent and position information. The tag will also label the messageas being a first generation message. Vehicles receiving the message willintroduce a random delay before subsequently transmitting the message inorder to avoid retransmitting a copy on top of one another. Any vehiclereceiving a first generation message will retransmit the message, butincreasing the generation number tag to show that the message is now asecond generation message. However, vehicles receiving second and higherorder generation messages will determine whether or not to retransmitthe message according to parameters that are set in a retransmissionalgorithm. Any message which is retransmitted will again have itsgeneration tag incremented. Thus, for instance, vehicles may retransmitthe message if the number of retransmissions is statistically low, thusensuring the best chance that the message will propagate backwards.Vehicles receiving a high statistical message rate will retransmitaccording to random parameters so that some vehicles retransmit and somevehicles do not. This ensures that the message continues at a highstatistical retransmission rate but does not grow so rapidly such as toswamp the system. Vehicles receiving messages where the generationnumber exceeds a predetermined limit, or where positional informationindicates that they are at a sufficient distance from the geographicalsource of the message that it is unlikely that the vehicle or followingvehicles are in danger will not retransmit the message or may modify themessage to send it as a lower urgency alert message.

Vehicles receiving early generation messages may retransmit the alarmmessage from their front facing antennas as well to roadsidetransceivers until such time as they receive an acknowledgement from ahighway control centre that the information has been received. Suchalerts reaching the relevant authorities can be used to place warningalerts in the messages within other roadside equipment that lie beforethe position of the accident or incident, and by the use ofauthorisation codes can be used to cancel the vehicle's daisy chain modeof message propagation. The parameters that control the algorithm'soperation may be modified from roadside sites allowing traffic controlor other authorities the ability to tailor the behaviour of the system,for instance to adapt it to different traffic flows or weatherconditions.

In rural areas, roadside transmissions may be infrequent. However, eachvehicle may intermittently transmit from its forward facing and backwardfacing transmitters. This has a safety feature of advertising thepresence of the vehicle to other vehicles, such that each vehicle canuse this information for collision avoidance calculations. Thetransmitters may also operate different power levels, i.e in a“whisper-shout” mode such that the approximate distance can bedetermined to near vehicles. Advantageously, each transmitter sends acode to indicate its power level of transmission. Individual codingschemes and random delay sequences allows many vehicle informationsystems in range of each other to operate concurrently withstatistically negligible chance of mutual interference.

Advantageously the in vehicle receiver is provided with a data port suchthat external devices can read received messages and transmit their ownmessages. Existing standards such as RS232 or USB may be used, althoughthe choice of interface is not important.

The data word, shown in FIG. 3, may support coding or message formatssuch as HTML. This may permit on board message or data systems, orportable devices such as lap top computers, to display or react to themessage content. This may be used in local advertising systems or thirdparty navigation systems or fleet management systems.

In urban areas, the distance between data links may be short - both intime and distance. Packet communication schemes may use the highbandwidth of the microwave system to transmit and receive data. Themicrowave link can be expected to support data rates of 10 M Bits persecond and above. This is far in excess of the data rates achievable bycellular telephone systems at present.

Given that only very few vehicles are within communication range with agiven roadside unit at any one time, the available bandwidth can be timeshared to give very high data-rate communications between a vehicle anda communications network. Data links to roadside units would need tosupport these data rates, which are easily within the capability offibre optic transmission systems.

The data exchange capability could be used to provide a telephone orvideo phone system, or in car entertainment on demand by download ofgames, music or video.

As noted hereinbefore, the system maybe arranged to give audio messagesto a driver which may indicate when he has exceeded the speed limit. Thesystem may also give intermittent messages confirming that it isfunctioning and may also give messages indicating when the driver isbelow the current speed limit but close to it. The driver may select thepercentage of the current speed limit which triggers such a message.Additionally the system may also be arranged to give positionalinformation if so requested as it passes each sign for example of theform “entering Kenton 5 miles south of Exeter on A379”. It is thuspossible to provide an in-vehicle data system, co-operating with aroadside network of transmitters to exchange data between thetransmitters and the car and optionally from the vehicle to the roadsideunits in order that speed limits and other useful data can be madereadily available.

The system naturally extends beyond the vehicle environment. Portabledata processing and display units—such as palm top computers andpersonal digital assistants—can receive data from local areatransmitters and display it to a user.

FIG. 4 schematically illustrates a pedestrian equivalent of the motorvehicle system illustrated in FIG. 1. It will be appreciated that manycomponents are shared by each system and that the vehicle and pedestriandistinction is in fact minimal.

A local data node, generally designated 65, comprises a data processorand receiver/transmitter 60 connected to an antenna 62 which may be amicrowave antenna, a radio antenna or an infrared or ultrasoniccommunications device. The antenna may be provided in the centre of a“cell” over which the transmissions from the antenna may be received.The size of the cell may can be controlled on the basis of positioning,power level and so may range from a few meters to hundreds of metersacross or more.

The data processor 60 interfaces with a memory 64 which stores the datato be transmitted. The data may include community information,advertisements from local stores, advertising from more distantcommercial concerns, menus from local restaurants and so on, and may beencoded such that it can be received and presented in a convenient form.Thus, the data may, for example, be presented in HTML format such that aportable computer running a standard browser format can display theinformation.

The use of a local memory 64 means that vast amounts of data can becached in the transmitter and can be repeatedly retransmitted. The dataprocessor 60 may also be in communication with a further communicationchannel, shown as a cable 50, but which may also be a radio link toanother computer such as that of an internet service provider. Thisfurther communication link can be used by a system administrator torefresh the data held in the memory 64 and also to supportbi-directional transfer of data. Thus a user having a suitably equippedportable computer or dedicated terminal may wish to access informationnot held in the loca cache—i.e. in memory 64. The user can request suchinformation and the data processor 60 can send a request for theinformation over the further communication link. Thus a user 70 can surfthe internet or establish other bi-directional communications, such ase-mail, telephone conversation or video link via the local data node 65.Given that the cells can be quite small, the number of users trying toestablish concurrent bi-directional communication is likely to remainsmall so each user should maintain a reasonable data rate. The use of adata cache within each fixed transmitter has several advantages. Animportant one is the fact that it acts to “decouple” the speedlimitations of the link 50 in the fixed telecommunications network fromthe speed of transmission to the user 70. It also enables data transferto the cache to be transmitted at whichever transfer rate is available.Data for the cache can be transferred via very slow links since littleof it will change over a period of days or weeks. When changes are made,these may typically involve only small sections of the data so again aslow data link will be adequate and will not prevent the total store ofdata within the cache from being continually up to date. The data whenthe cache can also be modified to allow urgent messages and updates tobe rapidly propagated. This is a useful distinction to the WAP enabledcellular telephone technology where each user is limited by the speed ofthe transmission of the link and for every sort of data communication,all of the data is transmitted individually to each user. In the systemdescribed herein, the speed of the link to the fixed telecommunicationnetwork is only relevant to the user when he wants to use the system asa link to this network, for example when using internet facilities orsending e-mails. Thus the use of the available transmission spectrum andbandwidth is much enhanced in systems constituting embodiments for thepresent invention.

The pedestrian and in vehicle systems may utilise the same display unit18. The unit 18 may sit in a docking station and communicate with thevehicle's data processor via an infrared data link or via directelectrical connection. The same unit 18 can communicate with the datanode 65 via its inbuilt IR Link, an inbuilt transceiver or viaconnection to an add-on module.

Such a system gives access to a variety of services and information. Italso provides a continuously available update of contextual informationrelated to the user's current geographical position.

Furthermore the system is robust since each local area transmitter/datanode 65 contains cached local information and can work autonomously if acentralised network computer fails.

The system can use the exceptional bandwidth of microwave communicationsystems to provide rapid internet access or video access. Furthermore,each transmitter may be subdivided into a plurality of zones—each beingcovered by its own antenna so as to further enhance its capability formulti-user access. Each zone, and indeed each transmitter, can engage incommunication of specific data to a specific user and consequentlyprovision must be made to hand over the data communications from onezone to a next or one transmitter to another as a user wanders around.However, technology of this type is already established for use withmobile telephones and does not constitute part of the present invention.

It is thus possible to provided a data system which can be used toprovide updatable information which is based on a user's geographicalposition. Thus a user may receive local adverts from shops and may evenquery local shops to obtain prices of goods or directions within a shopas to where to find the goods. The cell size can deliberately bemaintained small, for example 10 meters or so, such that information canbe very specific.

1. A vehicle information system comprising a receiver responsive tolocal data transmissions from roadside transmitters; a transmitter fortransmitting messages to another vehicle; a communications device forproviding at least one of audio and visual communication forcommunicating information to an occupant of a vehicle; and a dataprocessor arranged to receive signals from the receiver corresponding tothe local data transmissions from the roadside transmitters and to daisychain some of the signals it receives by re-transmitting them via thetransmitter.
 2. A vehicle information system as claimed in claim 1, inwhich the receiver has a narrow acceptance aperture such that it isresponsive substantially only to signal coming from a predetermineddirection with respect to the vehicle.
 3. A vehicle information systemas claimed in claim 2, in which the receiver's acceptance aperture isrestricted in the horizontal plane and can view from the horizontaltowards the vertical in the vertical plane.
 4. A vehicle informationsystem as claimed in claim 1, in which said messages include at leastone of messages generated by the vehicle warning of severe braking andmessages generated by the vehicle warning of adverse conditions.
 5. Avehicle information system as claimed in claim 4 further comprising adata processor responsive to an emergency deceleration signal andarranged to transmit a signal to following vehicles via the transmitterindicative that its vehicle is undergoing heavy braking.
 6. A vehicleinformation system as claimed in claim 1, in which said messages includedaisy chained messages.
 7. A vehicle information system as claimed inclaim 1, in which the data processor is arranged to generate a randomdelay period before retransmitting the signals.
 8. A vehicle informationsystem as claimed in claim 1, wherein an algorithm is employed withinthe data processor to enable the control of the geographical extent ofany daisy chain message.
 9. A vehicle information system as claimed inclaim 1, in which the daisy chain message includes a data tag includingposition information indicating a geographical source of the message,and in which the data processor is arranged to determine whether theposition information indicates that the system is a sufficient distancefrom the geographical source of the alarm message, and if so not toretransmit the alarm message or to modify the alarm message beforere-transmission.
 10. A vehicle information system as claimed in claim 9,in which the daisy chain message includes a generation number tag, andin which the data processor is arranged to determine whether or not tore-transmit the alarm message according to the generation number tag,and if so to increase the generation number tag before re-transmittingthe alarm message.
 11. A vehicle information system as claimed in claim1 wherein the transmitter is a rear facing transmitter for transmittingmessages to a following vehicle, and the system further comprises aforward facing transmitter; and a data processor arranged to receivealarm messages from the receiver, to daisy chain the alarm messages byretransmitting them via the rear facing transmitter, and to retransmitthe alarm messages from the forward facing transmitter to roadsidetransceivers.
 12. A vehicle information system as claimed in claim 11,in which the data processor is arranged to cancel the daisy chain modeof propagation in response to the receipt of an authorisation code. 13.A vehicle information system as claimed in claim 1 further comprising adata processor arranged to perform an arbitration algorithm if multiplebroadcasts are received simultaneously or near simultaneously.
 14. Avehicle information system as claimed in claim 1 in which the system isarranged to use messages from a preceding vehicle to carry out collisionavoidance calculations.
 15. A vehicle information system as claimed inclaim 1, in which the transmitter is arranged to intermittently transmitso as to advertise a presence of the vehicle to other vehicles.
 16. Avehicle information system as claimed in claim 15, wherein thetransmitter is a forward facing transmitter which is arranged tointermittently transmit so as to advertise the presence of the vehicleto preceding vehicles.
 17. A vehicle information system as claimed inclaim 1, in which the transmitter is arranged to transmit in a“whisper-shout” mode.
 18. A vehicle information system as claimed inclaim 1, in which the transmitter is arranged to send a code to indicateits power level of transmission.
 19. A vehicle information system asclaimed in claim 1, further comprising an onboard data processorarranged to use identity codes to distinguish between signals fromvehicles travelling in the same direction and those travelling in theopposite direction.
 20. A vehicle information system as claimed in claim1, in which the system is arranged to use a Doppler shift of the messagereceived from a transmitting vehicle to estimate the transmittingvehicle's speed and/or relative speed.
 21. A vehicle information systemas claimed in claim 1, in which the transmitter is arranged to act in aRADAR mode, using microwave travel time to another vehicle and back toprovide an estimate of range.
 22. A vehicle information system asclaimed in claim 21, wherein the signals are actively retransmitted withdata identifying the propagation delay introduced by the transmitter andreceiver of the other vehicle actively returning the signal.
 23. Avehicle information system as claimed in claim 1, wherein the system isadapted to actively retransmit signals with data identifying apropagation delay introduced by the transmitter and receiver.
 24. Avehicle information system as claimed in claim 1, in which the receiverlooks forward from the vehicle.
 25. A vehicle information system asclaimed in claim 1, in which the transmitter is a rear facingtransmitter for transmitting messages to a following vehicle.
 26. Avehicle information system as claimed in claim 1, in which the system isadapted to automatically transmit to the authorities when a speedviolation above a certain threshold has occurred.
 27. A vehicleinformation system comprising a receiver; a transmitter for transmittingmessages to another vehicle; a communications device for providing atleast one of audio and visual communication for communicatinginformation to an occupant of a vehicle; and a data processor arrangedto receive signals from the receiver and to daisy chain some of thesignals it receives by re-transmitting them via the transmitter; whereinan algorithm is employed within the data processor to enable the controlof the geographical extent of any daisy chain message; and wherein thealgorithm determines whether or not to re-transmit the daisy chainmessage according to a data tag within the daisy chain message.